Question

How to solve these question?

Answer 1

1a) Time = Distance/Speed 

t= 20/x seconds 

b) d=25m 
s= x+0.5 m/s 
t= d/s = 25/x+0.5 

c) total time = 6 seconds
therefore, 20/x + 25/x+0.5 = 6
make a common denominator of x(x+0.5):

(20(x+0.5) + 25x)/x(x+0.5) = 6
move the demoninator to the other side, and expand  to form:

20x+10+25x = 6x(x+0.5)
45x+10= 6x^2 +3x 
tidying it up (moving everything to one side)
6x^2 - 42x-10 = 0 
divide everything by 2
3x^2-21x-5= 0 (as required)

d) use quadratic formula to solve

e) therefore, what does x equal? 

hope this helps